Kaoru Tsuzuki

(Pb, La)(Zr, Ti)O3 Films by Multiple Electrophoretic Deposition/Sintering Processing

(Pb, La)(Zr, Ti)O3 films were prepared by multiple (electro-phoretic deposition/sintering) cycles, using fine crystalline powders, acetone, nitrocellulose and HNO3 as suspensions. Dense, strong films having a final thickness of 15~25 µm were formed reproducibly on platinum substrates. Due to tight contact between the film and rigid substrate, during firing, lattice constants of sintered films were 0.3~0.5% longer than those of bulk with the same composition. Reflecting these lattice expansions, the Curie temperature of sintered films shifted to higher temperature as compared to that of bulks with the same composition. All films with the composition 8/65/35 and 9/65/35 are ferroelectric and thus exhibit pyroelectric, and piezoelectric activities. These characteristics of the films are modified from those of the bulk form by crystal lattice distortion.

Dielectric properties of single crystals of Pb(zr,til - x) O3 solid solutions (x∼0.5)

The dielectric constants and spontaneous polarisations of Pb(ZrxTi1-x)O3 single crystals (x = 0.4 ∼ 0.5) were measured. On the tetragonal side, the low frequency (1 kHz) free and high frequency (50 MHz) clamped dielectric constants along the a-axis, ∊T11, ∊S11, increase remarkably on approaching the tetragonal-trigonal morphotropic phase boundary. At this phase boundary, an increase of the low frequency free dielectric constant along the c-axis, eT33, is observed, but the high frequency clamped dielectric constant along the c-axis, ∊S33 is independent of the composition. The temperature dependence of the free and the clamped dielectric constants were measured for x = 0.5 and 0.51 single crystals. Above the Curie temperature, equality between ∊S33 and ∊11 was not observed. The temperature dependence of the spontaneous polarisation Ps(x = 0.4) was measured by the Sawyer-Tower method. The room temperature value of Ps is 50 ∼ 55 μC/cm2 for x = 0.4 ∼ 0.5 single crystals.

Electrooptic Properties of Two-Stage Sintered (Pb1-xLax)(Zr, Ti)O3: X/65/35 Ceramics (X=6–9)

Several couditions for the 2-stage sintering method have been refined to improve the optical quality of (Pb, La)(Zr, Ti)O 3 (PLZT) ceramics, and electrooptical properties of fabricated PLZT ceramics with the composition of (6-9)/65/35 were examined. Ceramics which were obtained from mixed oxide (MO) powders exhibited better electrooptic characteristics (better transmittance, smaller residual birefringence, larger electrooptic coefficients) than those from coprecipitated (CP) powders under common processing conditions. For several compositions of MO-PLZT, smaller E c was attained, as compared with reported ones. A marked improvement in electrooptic coefficients (R=6.3×10 -16 m 2 /V 2 , V π =130 V, with 0.30 mm thickness)was also observed for Mo-PLZT (9/65/35) ceramics

The Growth of Ferroelectric Pb(ZrxTi1-x)O3 Single Crystals

Growing transparent single crystals of Pb(ZrxTi1-x)O3 with composition near x~0.5 was successfully done using the flux KF-PbF2-Pb3(PO4)2 (4: 5.6: 0.4 mole). Pale-yellow crystals of pseudo-cubic {100} faces with dimensions of 1 to 2 mm were obtained. Parallel to the c-plate crystal edges, a-domains were observed. Etch pits density observed on the single domain crystal surface is (3~7)×105/cm2. Etch pits were observed on the negative end of the polarization surface and these diagonal axes corresponded to the tetragonal a-axes.

Preparation and Characterization of (Pb,La)(Zr,Ti)O3 Composites (9/65/35 ∼ 6/65/35)

(Pb,La)(Zr,Ti)O3 (PLZT) composites between PLZT families were fabricated by a two-stage sintering method. The compositions selected in this study were (8/65/35 : 6/65/35) and (9/65/35 : 7/65/35). The internal structures of the composites which coexisted with endmembers components were examined using an optical microscope. The dielectric properties of the composites suggested the growth of an intermediate and the volume fraction was evaluated by a series connected three-layer capacitor model. Tc and Pr of the composites increased close to the corresponding values of pure PLZT as the mixing fraction approached 50%. Under the same conditions, the composites exhibited larger values of tan δ and Ec than the corresponding values of pure PLZT. For thickness vibrational mode, large k(0.35–0.50) and small Qm(8–25) are obtaind. These values of the composites are comparable with the corresponding values of (Pb,Ba)LaNb2O6 ceramics.

Measurement of Concentration in Particle Suspensions Using a Converged Ultrasonic Impulse with a Broad Frequency Bandwidth

As a method to measure the concentration and acoustical properties of fine particle suspensions, we proposed a new procedure using ultrasonic attenuation, which is based on the attenuation of ultrasonic waves passing through a liquid specimen. In order to carry out the experiment, we used a focused ultrasonic impulse with a broad frequency bandwidth using a plano-concave transducer instead of a continuous wave as is utilized in the conventional method. As specimens, we used some substances composed of fine particles, the acoustic properties or sizes of which differ. As a result, it was revealed that the particle concentration and acoustical properties could be instantaneously measured easily from the attenuation information in the frequency spectrum of ultrasonic pulses. It was also clarified that the plano-concave transducer had more useful features for the measurements than polyvinylidene fluoride (PVDF) transducers.

Chemical Preparations and Two-Stage Sintering of PLZT

Soft agglomerate, fine particle size and amorphous PLZT powders are prepared from nitrates solutions. The effects of postprecipitation processing (washing, drying, raw powder aging and calcining temperature) on powder characteristics and on final densification are examined. Solid state reactions occur above 500°C and both PLZT and PbO phase appear on XRD-profiles. The Crystalline states of these PLZT and PbO are subjected on the above processing. A two-stage sintering is made with various processed powders. The application of acetone washed-aged raw powder and of calcination below 700°C is promissing to obtain fine PLZT ceramics.

Dielectric Properties and Related Domain Structures of Aged PLZT 8/65/35

A lessening of loss tan δ and three types of dispersion by lowering the low frequency e, for as-sintered, aged PLZT 8/65/35 are observed. These aging phenomena can be explained by the unpolar phase stabilization whthin a polar region <Tc. Remarkable stabilization begins at ~60°C. This concept was confirmed by the observation of polar microdomains. Average dimmensions of microdomain were ~300 A for polished-annealed samples and ~100 A for as-sintered ones.

Sintering of (Pb, La)(Zr, Ti)O_3 in Ozone Atmosphere and Its Ferroelectric Properties

Sintering behaviors of (Pb, La)(Zr, Ti)O 3 (PLZT 8/65/35) ceramics in ozone atmosphere and their ferroelectric properties were investigated. In the early stage of sintering, the presence of ozone prompted the growth of crystallites and grains, and promoted densification. Ozone content dependence of these structural factors of ceramics influenced their optical transmittances, and ferroelectric and electrooptic properties. Marked improvement of electrooptic coefficients (R = 30 x 10 -16 m 2 /V 2 , V π = 10V with 0.40-mm-thick plate) was obtained for ceramics sintered at 1100°C for 24 h in an ozone-rich (180ppm) atmosphere, as compared with ozone-free ceramics.

Growth Conditions and Their Effects on Growth Features of Pb(Zr-Ti)O3 Single Crystals

Growth conditions,.growth parameters and their effects on growth features of Pb(Zr-Ti)O3 single crystals were examined using high-temperature 40KF-56PbF2-4Pb3(PO4)2 solution as a flux. Crystal habit, size and quality are sensitive to both growth conditions and parameters. Desirable crystals are grown from raw material rich solutions using a temperature gradient which the bottom of the crucible is hotter than the top, during cooling.